闭包怪异问题: 为啥这个闭包函数不缓存 count 值?

[Angela2022]

function createIncrement() { let count = 0; function increment() { count++; } let message = Count is ${count}; function log() { console.log(message); }

return [increment, log]; } const [increment, log] = createIncrement(); increment(); increment(); increment(); log(); // What is logged?

问题

1. 为啥 log()输出 Count is 0? increment 闭包 ha 函数为啥不缓存 count 的值?

2. 为啥把 let message = Count is ${count}移到 log 函数内就能输出 Count is 3? function log() { let message = Count is ${count}; console.log(message); }

[dvsilch]

message 定义在闭包外

[sweetcola]

message 没有变啊，message 是字符串，不会随 count 改变而改变。

[wiluxy]

你把 count 返回，打印一下，count 是有变的，问题在于 message 的值在定义的时候就确定了是 ’Count is 0‘，把 message 改为函数调用就符合你的预期了
```js
function createIncrement() {
let count = 0;
function increment() {
count++;
}

let message = () => `Count is ${count}`;

function log() {
console.log(message());
}

return [increment, log];
}

const [increment, log] = createIncrement();
increment();
increment();
increment();
log(); // Count is 3
```